NEBOSH EVALUATION EXAMS ANSWERS AND
QUESTIONS SET A+
✔✔Outline FOUR types of work activity associated with an oil platform that might
require permit to-work AND give a reason in EACH case for the requirement. - ✔✔Hot
Work
Hot Work Permits are generally applied to any type of work, which involves actual or
potential sources of ignition, and work for which there may be a risk of a fire and/or
explosion, or which involves the emission of toxic fumes from the application of heat.
Cold work
Cold work shall include but not be limited to the following: scaffolding, cleaning, over
side working, painting
Confined space entry
A confined space is any vessel, enclosure or compartment large enough to take a
person where the atmosphere may be dangerous or incompatible to a person entering
because of flammable/toxic gases and other substances or oxygen deficiency.
Isolation
An Isolation Certificate is required before any work can be started on process,
mechanical or electrical plant or equipment. An Isolation Certificate is also required
where access to the site of work is restricted or its safety is jeopardized by any adjacent
plant or equipment. An activity cannot commence until all the necessary isolation
requirements are in place
Diving
Diving certificate can be used to control the diving activity itself and to ensure that there
are no other activities taking place nearby which create unnecessary additional risks
e.g. over-side work, live firewater intake pumps.
,✔✔Identify TWO ways in which vapour clouds can be generated - ✔✔Sudden
depressurization
Rupture of vessel
Loss of containment
Uncontrolled buildup of pressure
✔✔Outline how a vapour cloud explosion can be generated - ✔✔Vapour cloud
explosion can be generated by;
Confined / unconfined generation
Vapour cloud explosions may arise from vaporization of a release of liquefied gas from
a ruptured vessel or pipeline
✔✔Identify the physical consequences of vapour cloud explosions - ✔✔Physical
consequences of vapour cloud explosions;
Overpressure
Fire & explosion
Resulting debris as airborne missiles
✔✔A pump containing flammable corrosive slurry has been stopped for maintenance.
An operator will prepare the pump for maintenance using a nitrogen supply, drain
header and collection vessel. Using this information;
Outline EIGHT risks to the operator when preparing the pump for maintenance. -
✔✔Asphyxiation due to displacement of 02
Fire
Explosion
Irritant/Corrosive substance
Incorrect isolation of valves
Incorrect Lock Out/Tag Out system
Lack of gas monitoring
, Burst pressure lines causing injury
✔✔Oil and gas installations use water for cooling and heating although it can be a
hazard in some situations.
Identify risks with water AND give a practical example in EACH case - ✔✔When stored
under pressure as in Fire lines and steam water lines
May contain bacteria if not circulated e.g. dead end pipe legs
May cause an unstable reaction when mixed with some hydrocarbons
✔✔Outline operational control measures that could minimize the risk of plant damage or
injury during start-up or shutdown of a process - ✔✔Shutdown:
Ensure work carried out under the controls of a PTW
All services are;
Stopped
Isolated
Drained down
Blanked
Empty & drain hydrocarbon facilities, with all liquids, gases and residues removed
leaving the plant safe to work on
Eliminate or control ignition sources
Suitable supervision of the operation
Certification of items that have been maintained or replaced
Start-up:
Establish all isolations reconnected, all blanks removed
Ensure all safety systems are operational
Ensure all systems are tested before start-up
Complete PTW
Emergency plan - in place
QUESTIONS SET A+
✔✔Outline FOUR types of work activity associated with an oil platform that might
require permit to-work AND give a reason in EACH case for the requirement. - ✔✔Hot
Work
Hot Work Permits are generally applied to any type of work, which involves actual or
potential sources of ignition, and work for which there may be a risk of a fire and/or
explosion, or which involves the emission of toxic fumes from the application of heat.
Cold work
Cold work shall include but not be limited to the following: scaffolding, cleaning, over
side working, painting
Confined space entry
A confined space is any vessel, enclosure or compartment large enough to take a
person where the atmosphere may be dangerous or incompatible to a person entering
because of flammable/toxic gases and other substances or oxygen deficiency.
Isolation
An Isolation Certificate is required before any work can be started on process,
mechanical or electrical plant or equipment. An Isolation Certificate is also required
where access to the site of work is restricted or its safety is jeopardized by any adjacent
plant or equipment. An activity cannot commence until all the necessary isolation
requirements are in place
Diving
Diving certificate can be used to control the diving activity itself and to ensure that there
are no other activities taking place nearby which create unnecessary additional risks
e.g. over-side work, live firewater intake pumps.
,✔✔Identify TWO ways in which vapour clouds can be generated - ✔✔Sudden
depressurization
Rupture of vessel
Loss of containment
Uncontrolled buildup of pressure
✔✔Outline how a vapour cloud explosion can be generated - ✔✔Vapour cloud
explosion can be generated by;
Confined / unconfined generation
Vapour cloud explosions may arise from vaporization of a release of liquefied gas from
a ruptured vessel or pipeline
✔✔Identify the physical consequences of vapour cloud explosions - ✔✔Physical
consequences of vapour cloud explosions;
Overpressure
Fire & explosion
Resulting debris as airborne missiles
✔✔A pump containing flammable corrosive slurry has been stopped for maintenance.
An operator will prepare the pump for maintenance using a nitrogen supply, drain
header and collection vessel. Using this information;
Outline EIGHT risks to the operator when preparing the pump for maintenance. -
✔✔Asphyxiation due to displacement of 02
Fire
Explosion
Irritant/Corrosive substance
Incorrect isolation of valves
Incorrect Lock Out/Tag Out system
Lack of gas monitoring
, Burst pressure lines causing injury
✔✔Oil and gas installations use water for cooling and heating although it can be a
hazard in some situations.
Identify risks with water AND give a practical example in EACH case - ✔✔When stored
under pressure as in Fire lines and steam water lines
May contain bacteria if not circulated e.g. dead end pipe legs
May cause an unstable reaction when mixed with some hydrocarbons
✔✔Outline operational control measures that could minimize the risk of plant damage or
injury during start-up or shutdown of a process - ✔✔Shutdown:
Ensure work carried out under the controls of a PTW
All services are;
Stopped
Isolated
Drained down
Blanked
Empty & drain hydrocarbon facilities, with all liquids, gases and residues removed
leaving the plant safe to work on
Eliminate or control ignition sources
Suitable supervision of the operation
Certification of items that have been maintained or replaced
Start-up:
Establish all isolations reconnected, all blanks removed
Ensure all safety systems are operational
Ensure all systems are tested before start-up
Complete PTW
Emergency plan - in place
